THE GYMNOTID EELS OF TROPICAL AMERICA. 195 



Summary. 



1. The power to regenerate lost portions of the caudal half and the anal region 

 is quite general throughout the family Gymnolidoe. Nineteen of the twenty-seven 

 species are known to possess this power of regeneration. 



2. The part regenerated is quite like the part lost, scales, fin, fin-rays, muscles, 

 and pigment being restored. 



3. Two species at least, G. carapo and E. virescens, regenerate the parts re- 

 moved very completely. 



4. Several species of the Sternarchince regenerate a complete caudal fin, 

 which may be larger and may contain more rays than the normal caudal, at what- 

 ever point the part has been removed. The caudal fin is regenerated without the 

 restoration of more than a small portion, if any, of the caudal peduncle. 



5. Experiments show injury to the caudal half to be of little consequence. 



6. The majority of the injuries foimd were in the caudal region. This locali- 

 zation of injury was noted particularly in the Sternopygince, in which the caudal 

 region bore about three-fourths of the injuries. 



7. The elongated tail and the extreme cephalad position of the viscera seem 

 to be protective adaptations. 



NOTE BY C. H. EIGENMANN. 



In a paper which appeared after the present contribution was offered for publi- 

 cation, Regan (The Classification of the Teleostean Fishes of the Order Ostario- 

 physi.-Cyprinoidea. Ann & Mag. Nat. Hist. (8), Vol. VIII, July, 1911, pp. 13-32) 

 recognizes four families and two subfamilies of the " Gymnotiformes " as follows: 



1. Rhamphichthyidse {Rhamphichthys) . 



2. Sternarchidse. 



Sternarchinse {Sternarchus, Sternarchogiton, Slernarchorhamphus, Sternarcho- 



rhynchus) . 

 Sternopyginse {Sternopygus, Steatogenys, Eigenmannia, Hypopomus). 



3. Gymnotidse (Gymnotus). 



4. Electrophoridse (Electrophorus) . 



